By Venkatachari Jagannathan Chennai, June 23 : A total of 1,660 MW of atomic power capacity belonging to Nuclear Power Corporation of India Ltd. (NPCIL) has been shut down largely for refuelling and maintenance in Southern India. India's atomic power company NPCIL has a total of 3,320 MW capacity in Tamil Nadu (2,440 MW) and Karnataka (880 MW). The units that are under shutdown are -- Kudankulam Unit 1-1,000 MW; 2 Units of Madras Atomic Power Station (MAPS)- 440 MW; Kaiga Atomic Power Station Unit 4-220 MW. On Tuesday 1,000 MW generation capacity located in Kudankulam Nuclear Power Station (KNPS) was shut down for refueling and annual maintenance while the atomic power plant in Kaiga was stopped for 'Reactor Protection Operated'. Speaking to IANS a senior NPCIL official on the condition of anonymity said the Unit 1 in KNPS was shut down for refuelling and maintenance purposes. "Normally a nuclear reactor of this size will have to be refuelled after 270-300 days of operation. One third of the 163 fuel bundle will be replaced," the official said. Alongside the refuelling of the reactor, the machines in the power island like turbine and others will also be overhauled. The refuelling of the Unit 2 was done this April and has been functioning well, the official said. On Tuesday, Unit 2 at KNPS generated 932 MW, while the three units in Kaiga were under operation and generated 626 MW. While one 220 MW unit at MAPS is not in operation for more than three years, the second unit was shut down for maintenance this April. The NPCIL is building four more 1,000 MW nuclear power plants in Kudankulam - Units 3-6. The construction of Units 3 and 4 is under progress while the construction work for Units 5 and 6 is expected to start soon. According to an official, construction work for 3 and 4 units was affected due to Covid-19 pandemic and the work is now in progress. (Venkatachari Jagannathan can be contacted at v.jagannathan@ians.in) /IANS